In accordance with the recent development of nanotechnology, a demand is growing for an extremely micro particle (hereinafter called as a single nanoparticle) of a single nanometer (1˜10 nm). In case of manufacturing the single nanoparticle with high accuracy, since a grinding method has limitations, a method for producing a single nanoparticle by growing a crystal has been developing recently. In this case, it is necessary to measure a diameter of a particle during a process of growing the crystal in real time in order to control, for example, a particle diameter.
As a method for measuring a diameter of a particle among analyzing particles known are various methods such as a laser diffraction method and a centrifugal sedimentation method, however, practically from a view point of a performance and a cost, a photon correlation method that is based on a dynamic scattering theory is one of the most effective methods in order to measure a diameter of a single nanoparticle.
A particle diameter distribution measurement device by the use of the photon correlation method based on the dynamic scattering theory irradiates the laser light on particles that are making the Brownian motion in a sample solution, receives the scattered light due to the particle by the use of a photoelectron multiplier, makes auto-correlation data based on a pulse obtained by shaping a waveform of an electric current signal output by the photoelectron multiplier and calculates particle diameter distribution of a particle group based on the auto-correlation data.
In accordance with the particle diameter distribution measurement device having the above arrangement, in case that the scattered light enters into the photoelectron multiplier due to, for example, a foreign material whose particle diameter in a sample solution is big, there might be a case that an overcurrent that is more than or equal to an allowable value is produced in the photoelectron multiplier. In case that the overcurrent is produced, since the photoelectron multiplier is desensitized and deteriorated, an absolute value of a negative high voltage applied to the photoelectron multiplier is decreased or applying the negative high voltage is ceased in order to halt the measurement at a time when the overcurrent is produced (for example, the patent documents 1 and 2).
In accordance with this kind of the particle diameter distribution measurement device, in case that the measurement is halted in midstream, time series data of a number of pulses that are continuous from initiation of the measurement is broken at the time. As a result of this, even though the measurement is restarted after this time, since there exists no time series data of the pulse number from the initiation of the measurement to the halt of the measurement due to the overcurrent, it becomes impossible to produce the auto-correlation data. Then, it becomes necessary for a user to restart the measurement of the scattered light from the beginning.